Abstract: Photonic technology plays an important role in the development of new medical diagnostic and therapeutic instruments. Readily available compact solid-state lasers and various types of light sources allow one to examine tissues in a clinical environment using new and emerging photonic technologies. The objective of this work is to provide theoretical and experimental procedure of laser optoacoustic imaging to address breast cancer diagnosis using thermo-acoustic imaging principles, where the analytical simulation and experimental results have been represented. The key task in photoacoustic imaging is to determine the electromagnetic absorption distribution from the measured photoacoustic data; i.e., to map the electromagnetic absorption heterogeneity of the tissue, propagation time and acoustic pulse duration which have been used to determine location and size of the tumor model. The analytical simulation has been analyzed using the spherical and plane wave models representing breast tumor, where the photoacoustic pulse presented from spherical tumor within the breast, has a radius of curvature of 0.3, 0.5, 1 and 1.5cm. The disk of irradiation is created by a 2cm laser spot on breast tissue phantom of 5cm-1 absorption coefficient. Nd:YAG laser operating with 1064nm wavelength and pulse energy of 75mj. The electromagnetic heating must be rapid enough to produce photoacoustic waves efficiently, therefore, the pulse width has been assumed to be a short laser pulse of 6ns. Simulation and experimental results of blood model are obtained for the cases of pressure waves which are induced by a 4mm laser spot on blood samples of 1, 3, 10 and 40cm-1 absorption coefficient, operating with the second harmonic generation 532nm wavelength, pulse width of 6ns and pulse energy ranging from 11.8 to 28.7mj. The photoacoustic waves which have been excited by thermoelastic expansion are detected by a piezoelectric transducer which has a diameter of active area of 10mm, frequency bandwidth > 50MHz and acoustic impedance 4.1´106 kg/m2s.